A Transformerless Active Voltage Quality Regulator With the Parasitic Boost Circuit

Voltage sags have always been a huge threat to sensitive industrial and commercial electrical consumers, and deep sags with long duration time are usually more intolerable. In this paper, a new topology of series-connected compensator is presented to mitigate long duration deep sags, and the compensation ability is highly improved with a unique shunt converter structure acting as a parasitic boost circuit that has been theoretically analyzed. Additionally, the proposed active voltage quality regulator is a cost-effective solution for long duration sags that are lower than 50% of the nominal voltage as it is transformerless compared with the traditional dynamic voltage restorer. High operation efficiency is ensured by applying the dc-link voltage adaptive control method. Analysis, along with simulation and experimental results, is presented to verify the feasibility and effectiveness of the proposed topology.